Memory loss is one of the most fundamental features of aging. The central focus of these experiments is the understanding of the decline in neuronal plasticity which must accompany and explain the failure of retention. A behavioral task performance in a spatial maze) has been identified which clearly distinguishes young from aged rats and which has also been shown to be dependent on the integrity of hippocampal tissue. Synaptic plasticity as a function of aging will be examined by kindling via hippocampal pathways, long-term potentiation of the relevant synapses, microelectrode analysis of kindling and analysis of transmitter receptor binding in hippocampal tissue. Electron microscopic analysis of synaptic structure and distribution in hippocampal dentate gyrus will be carried out and the results related to deficits in spatial memory and synaptic plasticity.